U.S. patent application number 17/467090 was filed with the patent office on 2021-12-23 for high temperature heater lamp.
The applicant listed for this patent is ARIZONA BOARD OF REGENTS ON BEHALF OF ARIZONA STATE UNIVERSITY. Invention is credited to Ivan Ermanoski, Xiang Gao, Ryan Milcarek.
Application Number | 20210400773 17/467090 |
Document ID | / |
Family ID | 1000005826114 |
Filed Date | 2021-12-23 |
United States Patent
Application |
20210400773 |
Kind Code |
A1 |
Ermanoski; Ivan ; et
al. |
December 23, 2021 |
HIGH TEMPERATURE HEATER LAMP
Abstract
A high temperature heater lamp including a ceramic envelope is
disclosed. The ceramic envelope is substantially infrared
transparent and is composed of a refractory ceramic. The heater
lamp also includes two lead wires communicatively coupled via a
filament. The filament is enclosed within the ceramic envelope,
which is evacuated. The heater lamp may include at least two
metallic IR shields within the ceramic envelope, at least one
located on either side of the filament. The filament may be
tungsten, a carbon filament, or molybdenum. At least one end of the
ceramic envelope may be sealed with a metal cap affixed to the
ceramic envelope by a high vacuum sealant. The heater lamp may be
configured to operate at above 1500.degree. C. The ceramic envelope
may have a wall thickness less than 1 mm thick.
Inventors: |
Ermanoski; Ivan; (Tempe,
AZ) ; Gao; Xiang; (Tempe, AZ) ; Milcarek;
Ryan; (Gilbert, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ARIZONA BOARD OF REGENTS ON BEHALF OF ARIZONA STATE
UNIVERSITY |
Scottsdale |
AZ |
US |
|
|
Family ID: |
1000005826114 |
Appl. No.: |
17/467090 |
Filed: |
September 3, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
17115685 |
Dec 8, 2020 |
11116043 |
|
|
17467090 |
|
|
|
|
62945835 |
Dec 9, 2019 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B 3/0038 20130101;
H05B 3/44 20130101; H01K 1/08 20130101; H01K 1/36 20130101; H01K
1/40 20130101; H05B 3/12 20130101; H01K 1/32 20130101; H01K 1/06
20130101 |
International
Class: |
H05B 3/00 20060101
H05B003/00; H05B 3/44 20060101 H05B003/44; H01K 1/06 20060101
H01K001/06; H01K 1/40 20060101 H01K001/40; H01K 1/32 20060101
H01K001/32; H01K 1/36 20060101 H01K001/36; H01K 1/08 20060101
H01K001/08 |
Claims
1. A high temperature heater lamp, comprising: a ceramic envelope
having an interior, the ceramic envelope composed of a refractory
ceramic that is substantially infrared transparent; a filament
composed of a refractory material and enclosed within the ceramic
envelope; a getter enclosed within the ceramic envelope; and two
lead wires communicatively coupled to each other via the filament;
wherein the refractory ceramic is alumina; wherein the interior of
the ceramic envelope is evacuated.
2. The high temperature heater lamp of claim 1, wherein at least
one end of the ceramic envelope is sealed with a metal cap.
3. The high temperature heater lamp of claim 2, wherein the metal
cap is affixed to the ceramic envelope by a high vacuum
sealant.
4. A high temperature heater lamp, comprising: a ceramic envelope
having an interior, the ceramic envelope composed of a refractory
ceramic that is substantially infrared transparent; a filament
composed of a refractory material and enclosed within the ceramic
envelope; a getter enclosed within the ceramic envelope; and two
lead wires communicatively coupled to each other via the filament;
wherein the interior of the ceramic envelope is evacuated.
5. The high temperature heater lamp of claim 4, wherein at least
one end of the ceramic envelope is sealed with a metal cap.
6. The high temperature heater lamp of claim 5, wherein the metal
cap is affixed to the ceramic envelope by a high vacuum
sealant.
7. The high temperature heater lamp of claim 4, further comprising:
at least two metallic IR shields within the ceramic envelope;
wherein at least one metallic IR shield is located on either side
of the filament.
8. The high temperature heater lamp of claim 4, wherein the heater
lamp is configured to operate at above 1500.degree. C.
9. A method for assembling a high temperature heater lamp,
comprising: communicatively coupling two lead wires to each other
via a filament composed of a refractory material; positioning the
filament within a ceramic envelope that is substantially infrared
transparent, the ceramic envelope comprising a refractory ceramic
and having an interior; and closing an end of the ceramic envelope
with a metal cap by bonding the metal cap to the ceramic envelope
with a sealant; wherein an expense of the ceramic envelope is
reduced by allowing the ceramic envelope to have a tolerance that
is compensated for by the sealant between the ceramic envelope and
the metal cap.
10. The method of claim 9, further comprising evacuating the
interior of the ceramic envelope.
11. The method of claim 10, wherein the sealant is a high vacuum
sealant.
12. The method of claim 9, further comprising filling the interior
of the ceramic envelope with an inert gas.
13. The method of claim 9, further comprising: bonding a copper
tube to one of the two ends of the ceramic envelope with the
sealant; evacuating the interior of the ceramic envelope; and
pinching the copper tube while the interior of the ceramic envelope
is evacuated, causing the copper tube to bond with itself and form
a cold weld, sealing the ceramic envelope.
14. The method of claim 9, further comprising positioning a getter
within the ceramic envelope.
15. The method of claim 9, wherein the refractory ceramic is
alumina.
16. The method of claim 9, wherein the refractory material
comprises tungsten.
17. The method of claim 9, wherein the filament is a carbon
filament.
18. The method of claim 9, wherein bonding the metal cap to the
ceramic envelope with the sealant comprises: applying a layer of
sealant to both the metal cap and the refractory envelope; mating
the metal cap with the refractory envelope; and curing the
sealant.
19. The method of claim 9, further comprising positioning at least
two metallic IR shields within the ceramic envelope such that there
is at least one metallic IR shield on either side of the
filament.
20. The method of claim 9, wherein the sealant is a resin sealant.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 17/115,685, filed Dec. 8, 2020 (published as
US20210176827), which claims the benefit of U.S. provisional patent
application 62/945,835, filed Dec. 9, 2019 titled "High-Temperature
Heater Lamp," the contents of each of which are hereby incorporated
by reference in their entireties.
TECHNICAL FIELD
[0002] Aspects of this document relate generally to high
temperature heater lamps.
BACKGROUND
[0003] The reduction reaction in thermochemical cycles requires a
high-density heat source, to meet its energy demand at high
temperature. Concentrating solar systems can cover this demand
sustainably. However, these systems include additional energy
losses (e.g. optical, re-radiation, etc.) that could reduce the
final conversion efficiency by 30-50%. In addition, to be
cost-effective, these systems often require large prototypes and
plants, which are capital-intensive and discourage the development
of the technology.
[0004] Driving a reduction reaction in thermochemical cycles with a
high-density heat source powered by a form of renewable energy
other than concentrating solar faces a different set of problems.
While the use of electric heaters may solve some of the
inefficiencies of concentrating solar, conventional high
temperature heaters, such as silicon carbide and molybdenum
disilicide, are expensive. These refractory ceramic materials are
used as heating elements. In addition to being expensive, they are
not chemically inert and have low power density, limiting their
applications. Additionally, while they can reach high temperatures,
they are slow to ramp up and down. This complicates their use with
intermittent power inputs directly from renewable sources such as
wind and solar.
[0005] Filament based heaters, conventionally enclosed in a quartz
envelope, are able to ramp up in temperature quickly. However,
these heaters are not able to reach the high temperatures needed
for an efficient thermochemical cycle. Quartz, while inexpensive,
has an operating limit of about 900.degree. C. in air, and is very
sensitive to exposure to some common chemicals (e.g. the sodium and
potassium transferred from a human touch can permeate a quartz
envelope and compromise the filament).
SUMMARY
[0006] According to one aspect, a high temperature heater lamp
includes a ceramic envelope having an interior. The ceramic
envelope is composed of a refractory ceramic that is substantially
infrared transparent. The heater lamp also includes a filament
composed of a refractory material and enclosed within the ceramic
envelope, and two lead wires communicatively coupled to each other
via the filament. The refractory ceramic is alumina, and the
interior of the ceramic envelope is evacuated.
[0007] Particular embodiments may comprise one or more of the
following features. The high temperature heater lamp may further
include at least two metallic IR shields within the ceramic
envelope. At least one metallic IR shield may be located on either
side of the filament. The refractory material may include tungsten.
The filament may be a carbon filament. The refractory material may
include molybdenum. At least one end of the ceramic envelope may be
sealed with a metal cap affixed to the ceramic envelope by an
ultra-high vacuum sealant. The heater lamp may be configured to
operate at above 1500.degree. C. The ceramic envelope may have a
wall thickness less than 1 mm thick.
[0008] According to another aspect of the disclosure, a high
temperature heater lamp includes a ceramic envelope having an
interior. The ceramic envelope includes a refractory ceramic that
is substantially infrared transparent. The heater lamp also
includes a filament composed of a refractory material and enclosed
within the ceramic envelope, and two lead wires communicatively
coupled to each other via the filament.
[0009] Particular embodiments may comprise one or more of the
following features. The interior of the ceramic envelope may be
filled with an inert gas. The interior of the ceramic envelope may
be evacuated. The high temperature heater lamp may further include
at least two metallic IR shields within the ceramic envelope. At
least one metallic IR shield may be located on either side of the
filament. The refractory ceramic may be alumina. The refractory
material may include tungsten. The filament may be a carbon
filament. The refractory material may include molybdenum. At least
one end of the ceramic envelope may be sealed with a metal cap. The
metal cap may be affixed to the ceramic envelope by a high vacuum
sealant. The heater lamp may be configured to operate at above
1500.degree. C. The ceramic envelope may have a wall thickness less
than 1 mm thick.
[0010] Aspects and applications of the disclosure presented here
are described below in the drawings and detailed description.
Unless specifically noted, it is intended that the words and
phrases in the specification and the claims be given their plain,
ordinary, and accustomed meaning to those of ordinary skill in the
applicable arts. The inventors are fully aware that they can be
their own lexicographers if desired. The inventors expressly elect,
as their own lexicographers, to use only the plain and ordinary
meaning of terms in the specification and claims unless they
clearly state otherwise and then further, expressly set forth the
"special" definition of that term and explain how it differs from
the plain and ordinary meaning. Absent such clear statements of
intent to apply a "special" definition, it is the inventors' intent
and desire that the simple, plain and ordinary meaning to the terms
be applied to the interpretation of the specification and
claims.
[0011] The inventors are also aware of the normal precepts of
English grammar. Thus, if a noun, term, or phrase is intended to be
further characterized, specified, or narrowed in some way, then
such noun, term, or phrase will expressly include additional
adjectives, descriptive terms, or other modifiers in accordance
with the normal precepts of English grammar. Absent the use of such
adjectives, descriptive terms, or modifiers, it is the intent that
such nouns, terms, or phrases be given their plain, and ordinary
English meaning to those skilled in the applicable arts as set
forth above.
[0012] Further, the inventors are fully informed of the standards
and application of the special provisions of 35 U.S.C. .sctn.
112(f). Thus, the use of the words "function," "means" or "step" in
the Detailed Description or Description of the Drawings or claims
is not intended to somehow indicate a desire to invoke the special
provisions of 35 U.S.C. .sctn. 112(f), to define the invention. To
the contrary, if the provisions of 35 U.S.C. .sctn. 112(f) are
sought to be invoked to define the inventions, the claims will
specifically and expressly state the exact phrases "means for" or
"step for", and will also recite the word "function" (i.e., will
state "means for performing the function of [insert function]"),
without also reciting in such phrases any structure, material or
act in support of the function. Thus, even when the claims recite a
"means for performing the function of . . . " or "step for
performing the function of . . . ," if the claims also recite any
structure, material or acts in support of that means or step, or
that perform the recited function, then it is the clear intention
of the inventors not to invoke the provisions of 35 U.S.C. .sctn.
112(f). Moreover, even if the provisions of 35 U. S.C. .sctn.
112(f) are invoked to define the claimed aspects, it is intended
that these aspects not be limited only to the specific structure,
material or acts that are described in the preferred embodiments,
but in addition, include any and all structures, materials or acts
that perform the claimed function as described in alternative
embodiments or forms of the disclosure, or that are well known
present or later-developed, equivalent structures, material or acts
for performing the claimed function.
[0013] The foregoing and other aspects, features, and advantages
will be apparent to those artisans of ordinary skill in the art
from the DESCRIPTION and DRAWINGS, and from the CLAIMS.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The disclosure will hereinafter be described in conjunction
with the appended drawings, where like designations denote like
elements, and:
[0015] FIG. 1 is a perspective view of a high temperature heater
lamp;
[0016] FIG. 2 is a cross-sectional view of a high temperature
heater lamp on a vacuum line; and
[0017] FIG. 3 is a cross-sectional view of a stand-alone high
temperature heater lamp.
DETAILED DESCRIPTION
[0018] This disclosure, its aspects and implementations, are not
limited to the specific material types, components, methods, or
other examples disclosed herein. Many additional material types,
components, methods, and procedures known in the art are
contemplated for use with particular implementations from this
disclosure. Accordingly, for example, although particular
implementations are disclosed, such implementations and
implementing components may comprise any components, models, types,
materials, versions, quantities, and/or the like as is known in the
art for such systems and implementing components, consistent with
the intended operation.
[0019] The word "exemplary," "example," or various forms thereof
are used herein to mean serving as an example, instance, or
illustration. Any aspect or design described herein as "exemplary"
or as an "example" is not necessarily to be construed as preferred
or advantageous over other aspects or designs. Furthermore,
examples are provided solely for purposes of clarity and
understanding and are not meant to limit or restrict the disclosed
subject matter or relevant portions of this disclosure in any
manner. It is to be appreciated that a myriad of additional or
alternate examples of varying scope could have been presented, but
have been omitted for purposes of brevity.
[0020] While this disclosure includes a number of embodiments in
many different forms, there is shown in the drawings and will
herein be described in detail particular embodiments with the
understanding that the present disclosure is to be considered as an
exemplification of the principles of the disclosed methods and
systems, and is not intended to limit the broad aspect of the
disclosed concepts to the embodiments illustrated.
[0021] The reduction reaction in thermochemical cycles requires a
high-density heat source, to meet its energy demand at high
temperature. Concentrating solar systems can cover this demand
sustainably. However, these systems include additional energy
losses (e.g. optical, re-radiation, etc.) that could reduce the
final conversion efficiency by 30-50%. In addition, to be
cost-effective, these systems often require large prototypes and
plants, which are capital-intensive and discourage the development
of the technology.
[0022] Driving a reduction reaction in thermochemical cycles with a
high-density heat source powered by a form of renewable energy
other than concentrating solar faces a different set of problems.
While the use of electric heaters may solve some of the
inefficiencies of concentrating solar, conventional high
temperature heaters, such as silicon carbide and molybdenum
disilicide, are expensive. These refractory ceramic materials are
used as heating elements. In addition to being expensive, they are
not chemically inert and have low power density, limiting their
applications. Additionally, while they can reach high temperatures,
they are slow to ramp up and down. This complicates their use with
intermittent power inputs directly from renewable sources such as
wind and solar.
[0023] Filament based heaters, conventionally enclosed in a quartz
envelope, are able to ramp up in temperature quickly. However,
these heaters are not able to reach the high temperatures needed
for an efficient thermochemical cycle. Quartz, while inexpensive,
has an operating limit of about 900.degree. C. in air, and is very
sensitive to exposure to some common chemicals (e.g. the sodium and
potassium transferred from a human touch can permeate a quartz
envelope and compromise the filament).
[0024] Contemplated herein is a high temperature heater lamp that
is able to achieve high temperatures, up to and possibly exceeding
1900.degree. C. These high temperature heater lamps (hereinafter
"heater lamp") are also able to heat and cool rapidly, with high
ramp up/down rates. Additionally, the heater lamps contemplated
herein have a higher power per unit heater area than conventional
heaters.
[0025] Some conventional heaters are able to reach high
temperatures, and some are able to heat and cool quickly, but none
of them are able to do both. Advantageously, the high-temperature
heater lamps contemplated herein are able to compete with the best
of both types, reaching the higher temperatures at the higher ramp
up rates.
[0026] Not only do the high-temperature radiant heater lamps
disclosed herein improve on the performance and power density of
conventional high-temperature heat sources, they do so in a less
expensive package. The heater lamp utilizes low-cost manufacturing
techniques and materials. In some cases, the cost of the
contemplated heater lamps are an order of magnitude less expensive
than conventional heaters that reach the same temperature
range.
[0027] The contemplated heater lamps are ideal for use with
thermochemical cycles. The heater lamp decouples the thermochemical
cycles from direct solar radiation, moving the heat source inside
the reactor itself and minimizing radiative heat loses.
Additionally, the heater lamp reduces substantially the capital
cost of the system, scales more flexibly, and has a fast response
suitable for intermittent and relatively unconditioned power
inputs, according to various embodiments. The contemplated heater
lamp may also open up applications that are not practical using
conventional high temperature electric heating technology, beyond
thermochemical cycles.
[0028] FIG. 1 is a perspective view of a non-limiting example of a
high temperature heater lamp. As shown, the heater lamp 100
comprises a ceramic envelope 102. Housed inside the ceramic
envelope 102 is a filament 104 communicatively coupled to two lead
wires 106. According to various embodiments, the interior 112 of
the ceramic envelope 102 is either evacuated or filled with an
inert gas, as will be discussed in greater detail with respect to
FIGS. 2 and 3, below.
[0029] Conventional high temperature heaters sometimes make use of
refractory ceramics as heating elements that are expensive, slow,
and have low power density. The heater lamps contemplated herein
comprise a ceramic envelope 102 that is composed of, at least in
part, a refractory ceramic 108 that is substantially transparent or
translucent in the infrared range of the electromagnetic spectrum.
In the context of the present description and the claims that
follow, substantially transparent means at least 60% transparent.
It should be noted that in some embodiments, the refractory ceramic
108 may be between 70% and 80%, and in other embodiments, the
transparency may be higher. This transparency permits radiant heat
to leave the heater lamp 100 without directly and substantially
heating the envelope 102, thereby enabling good heat transfer from
the heater lamp 100. Additionally, the ceramic envelope 102 is
impervious to gasses, in particular oxygen, according to various
embodiments.
[0030] The ceramic envelope 102 is composed of a ceramic material
able to withstand the operating temperatures of the enclosed
filament 104, as well as the strain of repeated heating and cooling
cycles. According to various embodiments, the ceramic envelope 102
may be composed of alumina. Most substances do not react with
alumina, which is able to withstand very high temperatures.
Advantageously, alumina does not conduct oxygen like some
refractory ceramics, and is substantially transparent in the
infrared range of the electromagnetic spectrum (e.g. 70%-90%,
etc.). Furthermore, alumina is inexpensive, and strong enough that
the ceramic envelope 102 may be constructed with thin walls,
further facilitating heat transfer.
[0031] Embodiments of the contemplated heater lamp 100 making use
of a ceramic envelope 102 composed of alumina have been shown to be
sufficiently robust as well as effective. For example, in one
specific embodiment, a ceramic envelope 102 composed of alumina was
able to withstand over seven hundred 200.degree. C. heating and
cooling cycles oscillating around 1500.degree. C., as well as reach
temperatures above 1700.degree. C.
[0032] Other examples of refractory ceramic 108 include, but are
not limited to, nitrides (e.g. ZrN, etc.), borides (e.g. HfB.sub.2,
etc.), oxides (e.g. early transition metal oxides, Y.sub.2O.sub.3,
ThO.sub.2, etc.), and other ceramics known in the art. In some
embodiments, the ceramic envelope 102 may also be chemically inert,
chemically stable (particularly in air), have a high melting point,
a large band gap, no oxygen vacancies in the crystal structure,
strong enough to withstand operation while also remaining thin
enough to permit good heat transfer, and/or impermeable to gas.
[0033] As shown, the heater lamp 100 also comprises a filament 104.
In the context of the present description and the claims that
follow, a filament is an active heating element composed of a
conductive refractory material 110. The filament 104 may have the
form of a wire, a ribbon, or any other shape known in the art. Some
embodiments may have a single filament structure, while other
embodiment may employ a filament 104 composed of multiple
structures, all joined at either ends. The filament 104 is
communicatively coupled to a pair of lead wires 106, as shown. The
use of a filament 104 in conjunction with a ceramic envelope 102
allows the heater lamp 100 to reach high temperatures with rapid
ramp up and down rates.
[0034] According to various embodiments, the filament 104 is
composed, at least in part, of a conductive refractory material
110. In some embodiments, the refractory material 110 is tungsten.
Tungsten has a long history of use in light bulbs, resulting in
highly developed techniques in shaping and using tungsten as a
filament, resulting in low cost. Other embodiments may employ one
or more carbon filaments, which can also be inexpensive. Other
examples of conductive refractory materials 110 include, but are
not limited to, molybdenum, tantalum, and other materials known in
the art that will not sublimate at the contemplated temperatures
(e.g. 1500.degree. C. and higher). While more expensive than some
of the other exemplary materials, tantalum may be advantageous in
embodiments of the heater lamp 100 used in environments having
significant vibrations, as tantalum filaments tend to be more
mechanically stable due to recrystallization properties not found
in the other materials.
[0035] FIG. 2 is a cross-sectional view along the central axis of a
non-limiting example of a high temperature heater lamp 100. As
shown, one end of the ceramic envelope 102 is sealed with a metal
cap 200, while the other end is sealed to a flange 214 coupled to a
vacuum line 206. According to various embodiments, the interior 212
of the ceramic envelope 102 may be evacuated. In some embodiments,
that vacuum 204 may be maintained by attaching the heater lamp 100
to a vacuum line 206, or other vacuum system, through a flange 214
affixed to the end of the ceramic envelope 102. In other
embodiments, the ceramic envelope 102 may be evacuated through an
evacuation tube sealed inside the envelope 102, passing through a
cap (not shown). According to various embodiments, the interior 212
of the ceramic envelope 102 may be evacuated to a pressure less
than 10.sup.-4 Pa. In some embodiments, the total pressure may be
less than 10.sup.-6 Pa. In some embodiments, the evacuation of the
ceramic envelope 102 may result in a partial pressure of oxygen
less than 10.sup.-10 Pa, and of water vapor less than 10.sup.-9
Pa.
[0036] The ceramic envelope 102 is sealed such that a vacuum or an
inert gas may be maintained within, to maintain the necessary
oxidizer-free environment. As shown, in some embodiments, one or
both ends may be sealed with a metal cap 200. As a specific
example, in one embodiment, the metal cap 200 may be composed of
stainless steel. In other embodiments, the metal cap 200 may be
composed of other metals known in the art. In still other
embodiments, the end cap may be composed of materials other than
metals, given that their thermal expansion is similar enough to
that of the ceramic envelope 102 that the seal, cap, and/or
envelope 102 are not compromised during the temperature cycling
anticipated for the heater lamp, which may vary depending on the
intended application and the refractory ceramic 108 used.
[0037] One of the difficulties in using a refractory ceramic 108 to
construct the envelope 102 is that, unlike quartz, forming the
envelope 102 with good tolerances usually requires processing the
envelope 102 after creation, which greatly increases the cost.
According to various embodiments, rather than increase the
manufacturing cost, the poor tolerances common to ceramics may be
dealt with using a sealant.
[0038] In some embodiments, the metal cap 200 (and/or flange 214)
may be affixed to the ceramic envelope 102 using a high or
ultra-high vacuum sealant 202. In some embodiments, the cap 200 may
be bonded to the envelope 102 using a resin sealant, such as a
silicone resin sealant. It should be noted that the size of the
sealant shown in FIGS. 2 and 3 is not to scale, and has been
exaggerated for clarity. According to various embodiments, a thin
layer of sealant 202 is applied to both surfaces (i.e. envelope,
cap) before they are mated and allowed to cure. High vacuum sealant
advantageously tends to remain slightly flexible even when cured,
preventing cracking or leaks, particularly when bonding two
materials with different coefficients of thermal expansion. As a
specific example, in one embodiment, the cap 200 and/or flange 214
may be bonded to the envelope 102 using KL-5 vacuum leak sealant,
from the Kurt J. Lesker Company.
[0039] As shown, in some embodiments, the heater lamp 100 may
further comprise at least two metallic infrared shields 210. In the
context of the present description and the claims that follow, an
infrared shield 210 is an object that is substantially impervious
to infrared radiation that is placed between the filament 104 and
the ends of the envelope 102 to prevent heat from the filament 104
from escaping the ends and damaging the colder parts of the heater
lamp 100. According to various embodiments, the heater lamp 100 may
be configured to keep the ends of the envelope relatively cool
(e.g. 200.degree. C., etc.) in comparison to the middle of the
heater lamp 100, where the filament 104 is located. The metallic
infrared shields 210 prevent the filament 104 from overly heating
the ends of the heater lamp 100, and helps direct the heat outward,
through the envelope 102 and into the desired target.
[0040] In some embodiments, the infrared shields 210 may be
metallic foils. As a specific example, in one embodiment, the IR
shields 210 may be foils composed of tantalum, which has desirable
mechanical and thermal properties that make it well adapted for use
as an IR shield 210. In some embodiments, there may be multiple
shields 210 on either side of the filament 104. In still other
embodiments, the heater lamp 100 may not have any infrared shields
210.
[0041] In some embodiments, the heater lamp 100 may be single
ended, having both lead wires 106 exit the same end of the envelope
102. In other embodiments, the heater lamp 100 may be double ended,
with one lead wire 106 exiting the envelope 102 at one end, and the
other lead wire 106 exiting the opposite end. See, for example, the
non-limiting examples shown in FIGS. 2 and 3.
[0042] According to various embodiments, the ceramic envelope 102
may be cylindrical tube. Such a shape is advantageous, as it is
well adapted to resisting the mechanical stress caused by the
thermal shock due to the heater lamp 100 ramping up or down in
temperature. Other embodiments may employ other geometries known
for their resistance to thermal shock, including geometries having
more than one filament 104. For example, in one embodiment, the
ceramic envelope 102 may resemble the partial merging of two
cylindrical envelopes, each having a filament 104. Those skilled in
the art will recognize that other shapes known to be robust against
temperature fluctuations and mechanical stress may also be
applied.
[0043] One of the advantages of constructing the envelope 102 from
a ceramic material is that, due to its mechanical strength, the
wall thickness 208 of the envelope 102 may be reduced, increasing
the efficiency of heat transfer without sacrificing durability. In
some embodiments, the ceramic envelope 102 may be constructed with
wall thickness 208 lower than any practical wall thickness for a
quartz envelope. In some embodiments, the wall thickness 208 of a
ceramic envelope 102 having a quarter inch diameter may be less
than 1 mm (e.g. 0.5 mm, 0.75 mm, etc.). Typical quartz tubes having
that same diameter have a wall thickness of at least 1 mm. In other
embodiments, the wall thickness 208 may be 1 mm, or more, depending
on the envelope diameter.
[0044] FIG. 3 is a cross-sectional view along the central axis of a
non-limiting example of another embodiment of a high temperature
heater lamp. Specifically, FIG. 3 shows an embodiment of the heater
lamp 100 that is stand-alone, not requiring connection to a vacuum
system or source of inert gas 304. This particular non-limiting
example is filled with an inert gas 304. In embodiments where the
operating temperature of the filament is below the point of
sublimation, a vacuum filled envelope 102 may be preferred, since
it would eliminate heat transfer to the envelope 102 through
convention. However, in embodiments making use of refractory
ceramics 108 that are rated for temperatures closer to the maximum
operating temperature of the filament 104, the use of an inert gas
304 may be advantageous.
[0045] The non-limiting example of a heater lamp 100 shown in FIG.
3 is stand-alone, meaning both ends have been sealed, and
connection to a vacuum system or source of inert gas is not needed.
As shown, the heater lamp 100 may further comprise a getter 306, to
absorb any residual oxidizing gas, or any gas that gets through the
seal, prolonging the life of the filament 104.
[0046] Those skilled in the art will recognize that there are a
number of ways the ceramic envelope 102 may be sealed while under
vacuum or filled with inert gas. For example, as shown, in some
embodiments the envelope 102 may be sealed with a cold weld 300,
where a pure copper tube 302, bonded to the envelope 102 with
sealant 202, is pinched while under vacuum, causing the metal to
bond with itself forming the cold weld 300, as is known in the art.
Those skilled in the art will recognize that other materials and
methods may be used to seal the ceramic envelope 102 while under
vacuum or filled with inert gas 304.
[0047] Where the above examples, embodiments and implementations
reference examples, it should be understood by those of ordinary
skill in the art that other high temperature heater lamp examples
could be intermixed or substituted with those provided. In places
where the description above refers to particular embodiments of a
high temperature heater lamp, it should be readily apparent that a
number of modifications may be made without departing from the
spirit thereof and that these embodiments and implementations may
be applied to other high temperature radiant heater technologies as
well. Accordingly, the disclosed subject matter is intended to
embrace all such alterations, modifications and variations that
fall within the spirit and scope of the disclosure and the
knowledge of one of ordinary skill in the art.
* * * * *